JP2001011763A - Thin layer non-woven fabric having good compression- recovering property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thin layer non-woven fabric having a good compression- recovering property, capable of exhibiting a good recovering property in its thickness after removing a stress even on leaving it in a state of being continuously applied with a compressing stress by a packaging, etc. SOLUTION: This thin layer non-woven fabric contains 5-95 wt.% elastic composite fiber constituted with a polyester polymer and a thermoplastic elastomer, and has <=5 mm thickness web, in which crossing points of the elastic composite fibers are adhered each other by hot melt adhesion, and >=1.05 fold fiber bundled density at least in the surface layer part of the non-woven fabric as compared with that of the inner layer part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin nonwoven fabric, and more particularly, to a method for recovering a thickness of a thin nonwoven fabric after the stress is removed even when the package is left in a state where a compressive stress is continuously applied. The present invention relates to a thin nonwoven fabric having good compression recovery properties.

[0002]

2. Description of the Related Art In general, nonwoven fabrics are often wound into long rolls or packed in multiple layers, that is, packed under compressive stress, and are often transported, distributed, and stored as they are.

Therefore, when the nonwoven fabric in such a state is unpacked, the compressive stress is not sufficiently recovered, the thickness and density set at the time of manufacture are changed, and the center of the roll is closer to the outer periphery than to the outer periphery. Due to the high pressure, there is a drawback that the thickness and density tend to vary in the longitudinal direction of the nonwoven fabric.

In particular, as a filter, a packaging material, a pulp base fabric, a top sheet or a secondary sheet of a sanitary material, a garment core material, a batting for a garment, a shoulder pad, a base material of a pat material for an inner material, or a cushion material. In a thin non-woven fabric having a thickness of less than 5 mm, this phenomenon occurs remarkably, causing problems such as a reduction in the yield as a product.

As a method for solving such a problem, it is conceivable to reduce the amount of winding when the nonwoven fabric is wound into a roll. However, the productivity may decrease due to an increase in the number of roll changes in the production process. There are problems such as an increase in transportation, distribution, and storage costs, and the fact is that sufficient measures have not been taken.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for recovering the thickness after the stress is removed even when the package is left in a state where a compressive stress is continuously applied by packing or the like. It is to provide a good thin nonwoven fabric.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems of the prior art, and as a result,
In a thin nonwoven fabric containing an elastomer component, when increasing the fiber bundle density of the surface layer portion from the fiber bundle density of the inner layer portion,
We have found that the above problems can be solved.

Thus, according to the present invention, an elastic conjugate fiber composed of a polyester polymer and a thermoplastic elastomer is contained in an amount of 5 to 95% by weight, and the thickness at which the intersections of the elastic conjugate fibers are thermally fused to each other is reduced. A thin nonwoven fabric having a thickness of less than 5 mm, wherein the fiber convergence density in at least one surface portion of the nonwoven fabric is 1.05 times or more the fiber convergence density of the inner layer portion.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The core-sheath composite fiber used in the present invention is formed of a thermoplastic elastomer and an inelastic polyester polymer. At this time, the former is at least one of the fiber surfaces.
/ 2 are preferred. It is appropriate that the former and the latter are in a composite ratio of 30/70 to 70/30 in terms of weight ratio.

The form of the elastic composite fiber may be either side-by-side or sheath-core type, but the latter is preferred. In this sheath-core type, inelastic polyester is the core, but this core may be concentric or eccentric. In particular, the eccentric type is more preferable since a spiral crimp is developed.

The thermoplastic elastomer is preferably a polyurethane elastomer or a polyester elastomer.

The polyurethane elastomer includes a low melting point polyol having a molecular weight of about 500 to 6000, such as dihydroxy polyether, dihydroxy polyester, dihydroxy polycarbonate, dihydroxy polyester amide, and an organic diisocyanate having a molecular weight of 500 or less, such as p, p'-. Diphenylmethane diisocyanate, tolylene diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, 2,6-diisocyanatomethylcaproate, hexamethylene diisocyanate, etc., and a chain extender having a molecular weight of 500 or less, for example, glycol, amino alcohol or triol And the polymer obtained by the reaction with

Among the above-mentioned polymers, particularly preferred as the polyol is polyurethane using polytetramethylene glycol or poly-ε-caprolactone or polybutylene adipate. In this case, p, p'-diphenylmethane diisocyanate is preferable as the organic diisocyanate, and 1,4-butanediol is preferable as the chain extender.

On the other hand, examples of the polyester elastomer include a polyetherester copolymer obtained by copolymerizing a thermoplastic polyester as a hard segment and a poly (alkylene oxide) glycol as a soft segment.

More specifically, terephthalic acid, isophthalic acid, phthalic acid, naphthalene-2,6-dicarboxylic acid,
Naphthalene-2,7-dicarboxylic acid, diphenyl-4,
Aromatic dicarboxylic acids such as 4'-dicarboxylic acid, 1,4-
Alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid,
Succinic acid, oxalic acid, adipic acid, sebacic acid, dodecandic acid, at least one dicarboxylic acid selected from aliphatic dicarboxylic acids such as dimer acid or ester-forming derivatives thereof, and 1,4-butanediol; Aliphatic diols such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, neopentyl glycol, decamethylene glycol or 1,1-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclo At least one diol component selected from an alicyclic diol such as decane dimethanol or an ester-forming derivative thereof, and polyethylene glycol or poly (1,1) having an average molecular weight of about 400 to 5,000. And / or 1,3-propylene oxide) glycol, poly (tetramethylene oxide) glycol, a copolymer of ethylene oxide and propylene oxide, and a copolymer of ethylene oxide and tetrahydrofuran. And the like.

However, from the viewpoints of adhesiveness, temperature characteristics and strength, a block copolymer polyetherester using polybutylene-based terephthalate as a hard segment and polyoxybutylene glycol as a soft segment is preferred.

In this case, the polyester portion constituting the hard segment is polybutylene terephthalate in which the main acid component is terephthalic acid and the main diol component is a butylene glycol component. Of course, a part (usually 30 mol% or less) of this acid component may be substituted with another dicarboxylic acid component or oxycarboxylic acid component, and similarly, a part of the glycol component (usually 30 mol% or less) is butylene. It may be substituted with a dioxy component other than the glycol component.

The polyether moiety constituting the soft segment may be a polyether substituted with an oxyalkylene unit other than the oxybutylene unit.

The polymer may also contain various stabilizers, ultraviolet absorbers, thickening and branching agents, matting agents, coloring agents, and other various improvers, if necessary.

The degree of polymerization of the polyester elastomer is preferably in the range of 0.8 to 1.7, particularly 0.9 to 1.5 in intrinsic viscosity. If the intrinsic viscosity is too low, the heat fixation point formed by the heat treatment may be easily broken. On the other hand, if the viscosity is too high, the elastomer does not easily flow at the time of heat fusion, and it is difficult to form a strong heat fixing point at the intersection of the elastic composite fibers.

The melting point of the thermoplastic elastomer is preferably lower than the melting point of the inelastic polyester polymer described later by 30 ° C. or more. The melting point of the thermoplastic elastomer is preferably, for example, a temperature in the range of 130 to 200C.

If the difference in melting point is less than 30 ° C., the heat treatment temperature during the fusing process becomes too high, so that stable production may be difficult, and the mechanical properties of the inelastic polyester polymer may be reduced. There are cases. If the melting point of the thermoplastic elastomer is not clearly observed, the melting point is replaced with the softening point.

On the other hand, as the non-elastic polyester polymer, polyethylene terephthalate, polybutylene terephthalate, poly-1,4-dimethylcyclohexane terephthalate, polypivalolactam or a copolymer ester thereof are used. Polybutylene terephthalate which is excellent in recovery is more preferable.

The single fiber fineness of the elastic conjugate fiber composed of the polyester polymer and the thermoplastic elastomer is preferably in the range of 0.5 to 100 denier. If the single-filament fineness is less than 0.5 denier, the card spinnability in the nonwoven fabric manufacturing process will be poor, and if it exceeds 100 denier, the entanglement of the web will be poor, and the texture as the nonwoven fabric may be reduced.

It is necessary that the mixing ratio of the above-mentioned elastic composite fiber is 5% by weight or more and 95% by weight or less. 5% by weight
If it is less than 10, the number of heat fixation points formed is small, and morphological stability due to compression and the like, and strength as a nonwoven fabric product are reduced. Further, there is a problem that the processability is deteriorated due to a decrease in strength. On the other hand, when the mixing ratio exceeds 95% by weight, the material becomes coarse and hard in texture.

In the present invention, the intersections of the elastic conjugate fibers are heat-sealed with each other to form a nonwoven fabric, and the fiber convergence density of at least one surface layer of the nonwoven fabric is one of the fiber convergence density of the inner layer portion. 0.05 times or more, that is, the fiber bundle density ratio (surface layer / inner layer) between the surface layer portion and the inner layer portion needs to be 1.05 or more.

By increasing the fiber convergence density of the surface layer, the fuzz on the surface of the nonwoven fabric is reduced, and when stored in a roll, when the surface layers of the nonwoven fabric come into contact with each other, the fibers of the surface layer are bonded to each other inside the nonwoven fabric. It can be suppressed from entering.

That is, when the fiber convergence density ratio between the surface layer portion and the inner layer portion is less than 1.05, the fluff of the surface layer portion of the nonwoven fabric increases, and when the surface layer portions of the nonwoven fabric come into contact with each other, the fiber of the surface layer portion is reduced. A phenomenon is seen in which the fibers mutually enter the nonwoven fabric and are wound and closed by friction between the fibers when wound into a roll.

When the center portion of the roll is rolled up and closed, the thickness of the nonwoven fabric at the center portion decreases. When the nonwoven fabric is released from the roll shape, the nonwoven fabric located at the central portion and the nonwoven fabric located at the surface portion are removed. Compression recovery is different, and causes uneven thickness of the product.

As a method of increasing the fiber convergence density of the surface layer portion of the thin nonwoven fabric higher than that of the inner layer portion, a hot air is strongly blown in a heat treatment step of heat-sealing the elastic conjugate fibers, and the fibers of the outer layer portion are flattened to reduce the bulk. The method of giving the density difference by doing, the method of giving the density difference by strongly tangling the surface of the web and suppressing the bulk of the fiber when performing the fiber entanglement by the needle punch, and giving the nonwoven fabric a certain gap There is a method of suppressing the bulk of the fiber in the surface layer by treating with a heat calender roller.

The present invention is directed to a thin nonwoven fabric having a thickness of less than 5 mm. When the thickness is 5 mm or more, variations in thickness and density hardly occur.

The average density of the thin nonwoven fabric of the present invention is 0.01
It is preferably from 0.05 to 0.05 g / cm ³ . When the density is less than 0.01 g / cm ³ , the strength of the nonwoven fabric decreases,
Characteristics required for various uses such as hiding properties and heat retention properties cannot be obtained. On the other hand, if the density exceeds 0.05 g / cm ³ , the flexibility of the nonwoven fabric is lost and the weight increases.

[0033]

The present invention will be described in more detail with reference to the following examples. In addition, each physical property in an Example was measured by the following method.

(1) Fiber Concentration Density Ratio A thin nonwoven fabric is impregnated with paraffin, then cut from the thickness direction, and an electron micrograph of the cut surface is taken. From this photograph, the number of cut ends of the constituent fibers on the cut surface of the thin nonwoven fabric is counted, and the fiber bundle density of the surface layer portion and the inner layer portion is determined. The fiber bundle density ratio was calculated by the following equation. The surface layer portion is a portion corresponding to 20% of the total thickness from the surface of the nonwoven fabric toward the center, and the inner layer portion is 40 to 60% of the total thickness from the surface of the nonwoven fabric toward the center. %.

[0035]

(Equation 1)

(2) Compression recovery under static load A load of 50 g / cm ² was applied to the thin nonwoven fabric,
After leaving for a period of time, the change in thickness when the load is removed is measured, and the compression recovery rate is determined from the following equation. In addition, thickness is 0.
The measurement was performed with an initial load of 5 g / cm ² .

[0037]

(Equation 2)

(3) Average density of nonwoven fabric The average density was calculated from the basis weight and thickness of the nonwoven fabric according to the following formula.

[0039]

(Equation 3)

(4) Recoverability of Thickness after Packing 200 m of the thin nonwoven fabric is wound into a roll and left for 24 hours, and then the roll is opened. Was evaluated by comparing the thickness of the thin non-woven fabric at the end of winding of 1 m. The evaluation criteria are as follows. ：: Roll surface thickness−roll center thickness <1 mm Δ: Roll surface thickness−roll center thickness <1.5 m
mx: thickness of roll surface-thickness of roll center portion ≥ 1.5 m
m

Example 1 Single fiber fineness: 6.0 denier
A polyethylene terephthalate short fiber having a hollow round cross section with a fiber length of 64 mm, a number of crimps of 9 / inch and a crimp rate of 13%, a polyetherester elastomer having a melting point of 151 ° C as a sheath component, and polybutylene terephthalate as a core component. After mixing with a core-sheath type elastic composite short fiber having a single fiber fineness of 6 denier and a fiber length of 51 mm in a weight ratio of 50:50, the mixture is opened with a hopper feeder, opened with a roller card, and then with a cross layer of 100 g / weight. m ² and a thickness of 3 mm (average density 0.033 g / cm ³ ).

Then, a temperature of 200 ° C. and a wind speed of 2 m
/ Sec, and heat-treated for 20 seconds to obtain a thin nonwoven fabric in which the intersections of the elastic composite short fibers and the intersections of the polyethylene terephthalate short fibers and the elastic composite short fibers were heat-sealed. Table 1 shows the physical properties of the obtained thin nonwoven fabric.

[Comparative Example 1] In Example 1, the temperature of the hot air was set to 200 ° C., and the wind speed was set to 0.3 m / sec.
The procedure was performed in the same manner as in Example 1 except that the heat treatment was performed for 2 seconds. Table 1 shows the physical properties of the obtained thin nonwoven fabric.

Comparative Example 2 The procedure of Example 1 was repeated, except that isophthalic acid copolymerized polyester having a melting point of 110 ° C. was used as the sheath component and polyethylene terephthalate was used as the core component. Table 1 shows the physical properties of the obtained thin nonwoven fabric.

Comparative Example 3 An experiment was carried out in the same manner as in Example 1 except that the mixing ratio of the polyethylene terephthalate short fibers and the elastic composite short fibers was 98: 2. Table 1 shows the physical properties of the obtained thin nonwoven fabric.

[0046]

[Table 1]

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasuyuki Yamazaki 3-4-1, Amihara, Ibaraki-shi, Osaka Teijin Limited Osaka Research Center F-term (reference) 4L041 BA02 BA05 BA21 BA49 BA59 BC17 BD03 BD11 CA08 CA16 DD01 DD05 DD14 4L047 AA21 AA27 AA28 AB02 AB09 BA09 BB06 BB09 CB01 CB10 CC01 CC03 CC06 CC12

Claims (4)

[Claims] 1. A thin layer having a thickness of less than 5 mm, comprising 5 to 95% by weight of an elastic conjugate fiber composed of a polyester polymer and a thermoplastic elastomer, wherein intersections of the elastic conjugate fibers are heat-sealed to each other. A thin nonwoven fabric, wherein a fiber bundle density of at least one surface layer portion of the nonwoven fabric is 1.05 times or more of a fiber bundle density of an inner layer portion. 2. The nonwoven fabric has an average density of 0.01 to 0.05.
g / in cm ^3, and a thin layer non-woven fabric of claim 1, wherein the compression recovery rate under a static load of 50 g / cm ² is 30% or more. 3. The thin nonwoven fabric according to claim 1, wherein the thermoplastic elastomer is a polyester elastomer. 4. The thin nonwoven fabric according to claim 1, wherein the polyester polymer is polybutylene terephthalate.